Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/28/1999
Publication Date: N/A
Interpretive Summary: Accurate grain yield measurement within a field is necessary in farm management. This information is used to vary the application rates of seeds, chemicals, fertilizers, etc. in order to optimize the grain yield. In order to confirm that the yield monitors perform well in measuring the grain yield, a laboratory test stand was developed. The grain flow was simulated and the grain flow-rates were measured with both a yield monitor and an electronic scale. The scale was used as a reference for the yield monitor. The tests showed that the yield monitor could measure the grain flow accurately if the yield monitor is calibrated according to the specifications. The performance of the yield monitor was found to be reasonable if the grain flow was steady. However, the yield monitor was less accurate if the grain flow-rate changed suddenly during the experiments. Sudden change is common in field operations since there is a natural yield variability in a field. The conclusion from this study is that producers can improve the yield monitor's accuracy in the field by averaging the yield data over short distances instead of using individual measurements done by the yield monitor.
Technical Abstract: Response of a yield monitor was compared to that of an electronic scale under laboratory operating conditions. Instantaneous yield data were used to make inferences about the behavior of the yield sensor. The yield sensor had an immediate response to sudden changes in corn flow when step inputs and transients were applied. The average percent error at constant flow rates was 2.1%. The average error increased to 3.2% and 4.3% when step inputs and transients were applied. Based on total weight comparisons, the yield monitor's overall average accuracy was within the reported accuracy range (+/ 4%) while the maximum errors were larger than 5%. The flow rate range incorporated into the calibration was found to be the most important factor in achieving better accuracies. Because of the fluctuations in instantaneous yield measurements, a single data point did not correlate well with the actual grain flow rate. Averaging over several seconds usually provided more reliable estimations for the grain flow rate.